Thameslink is a 24 hour train service This route would be set in 2016, when both the Class 319 and 700 were operated. It would feature the Main Line from Luton and Stevanage to East Croydon, with the Wimbledon Circle featured (as far as wimbledon), along with the Sevenoaks Line Stock: Class 319 The Class 319 is a Dual Voltage EMU that Operated on Thameslink from its opening in 1988 (i think) to 2017, when they were replaced by the Class 700 Class 700 The Class 700 is a DVEMU the operates the thameslink since 2015
Excellent idea and why not send them through the BML that way you can operate to Brighton via Gatwick Airport to London St Pancras Kings Cross underground Thameslink platforms. Your suggestion makes BML heavy traffic thanks to Thameslink. At London Bridge station where your suggestion joins with the Brighton main line up screen will say do you like to continue to Brighton yes or no? Yes Brighton main line for you assuming you purchase the DLC but No you have the option of return to main menu free roam scenarios
Okay then so your suggestion combined with BML makes Thameslink Brighton East Croydon Luton Airport service.